diagonal dilemma

[Timbo32]

Hi all,

i recently got a cheapish refracter it is an older skylux say 6-8 years old and it works great!

but i noticed that the diagonal was really dirty so i unscrewed the four screws on the underside

and the mirror came out no problems...

i cleaned it no problems it came up great no streaks

put it all back together no problems!!

looking at jupiter the other night and the clarity was great BUT...

around jupiter there was a brightish halo, it made the sky around jupiter milky in the halo

but outside the halo the sky was black as normal?

not sure what has happened!!!

Clear Skies Tim

[jonathan]

That probably just indicates that you had some dew on your optical surfaces, either the eyepiece, diagonal, or objective lens; it can happen with any scope but is more obvious on refractors and SCTs (because you can see the outer glass surfaces more easily).

It could also have been a thin layer of cloud that you couldn't see against the black sky.

[baggywrinkle]

What did you use to clean it?

I would use a pure soap such as an unperfumed baby soap, it does not leave deposits.

Wash first and gently dry with non linting tissue (non scratchy and no fibres)

Leave it in open air to dry.

It could be whatever you cleaned with has left a smear..

My only other thought is if you take a diagonal apart and put it together again, but over tighten on one point does it bend or alter the light path reflecting off the mirror?

[michael.h.f.wilkinson]

One simply problem could be the sky itself. I have seen halos around bright objects with squeaky-clean optics, simply due to thin high haze. It happens in autumn a lot, I find (that or solid cloud )

[Timbo32]

Hi baggywrinkle I cleaned the diagonal with a air blaster and when all the dusty bits were gone i wiped with a micro fibre cloth as i was worried if

i used soap it would leave streaks or residue. it looked really clean no streaks etc. will also check that im not over or under tightening the

diagonal and warping it?

Hi jonathan it wasnt dew because i thought that(Great minds!)and when i checked... Dry as a bone! plus i think it was too cold for dew!!!

everything was left outside the back door (where i observe) to cool for 30 mins as i always do

hadnt thought of high thin cloud, will have to take another look next year when we next have clear skies !!!

Thanks everyone for your help will report back let you know if any of the above has helped!

Clear Skies Tim

[baggywrinkle]

I recommended pure soap as I used to use it to clean dead weight piston gauges which had  very fine clearances and normal detergent would leave traces that could seize up an air bearing cleanace.

[michael.h.f.wilkinson]

I must say I am worried about the idea of pure soap. It could still leave a residue, and I do not know the pH of it, so it leaves me worried. If used, I would rinse thoroughly with distilled water to be sure to leave no residue.